**Instructions:**

In the table, the letters A, B, C, and D are placed in the rows and columns. Each letter represents one unique digit from 1 to 9. Next to each row and under each column there is the sum of the numbers in the relevant row or column. Your task is to find out what digits are hidden behind the letters A, B, C and D, and when there is no sum in a row or column, calculate this sum.